There Goes the Sun

VIEW FROM SPACE. Japan's YOHKOH satellite captured three series of images, such as this animation, of the moon moving across the sun's disk. The pictures are made from the sun's emissions of x-rays. Scientists hope to gain important insights by analyzing the changes in the radiation as the edge of the moon moves across solar "hot spots."

Image: GOES

MOONSHADOW. GOES, for Geosynchromous Operational Environmental Satellite, snapped a series of images as the dark "zone of totality" swept across the Pacific, Carribbean and Atlantic Oceans. Details of the path of the eclipse can also be seen on the accompanying map.

For millennia, humans have stared in wonder and awe as the moon's shadow briefly blocked out the sun. But there is still much to be learned--and the total solar eclipse that swept across the Caribbean on February 26 is likely to be the most closely observed ever. Astronomers and physicists aimed telescopes and other high-technology instruments at the sun's corona during the eclipse hoping to find new clues to the engine that drives our solar system.

The solar eclipse, billed as the "biggest" since the eclipse of July 1991, was visible as the moon's shadow blocked the disk of the sun in a band that began just below the Equator in the South Pacific, passed over South America and arced across the Atlantic toward North Africa. Although the skies dimmed far to the north (20 percent in New York City) and south, the impressive and ever mysterious solar corona was only visible in the narrow zone of total eclipse.

Image: NASA

ECLIPSE CHRONOLOGY. As an eclipse progresses, the moon's shadow gradually obscures more and more of the sun's disk, forming an ever-narrowing crescent. In the final moments, the last light of the sun bursts out, creating a display that looks like a diamond wedding ring and reveals "Bailey's Beads," bright spots created as the last light spews forth from valleys in the lunar mountains. During totality, the corona appears as a complete ring. The process reverses as the moon moves on.

During the fleeting three or four minutes of totality, scientists made observations from ground stations and research aircraft flying out of Panama. Meanwhile, the Solar and Heliospheric Observatory (SOHO) satellite operated by the National Aeronautics and Space Administration and a Japanese satellite called YOHKOH recorded new data from space. GOES, an Earth-sensing satellite, tracked the passage of the moon's shadow as it sped from west to east across the southern latitudes.

One team of scientists chased along the path of the eclipse in a specially instrumented C-130 Hercules aircraft. Flying in an unpressurized cabin at 18,000 feet, their goal was to detect the faint spectral line of ionized silicon in the sun's corona, or outer atmosphere. "It may prove to be the most sensitive indicator of coronal magnetic field strengths available to researchers," said National Center for Atmospheric Research physicist Philip Judge.

Several instruments on the SOHO satellite gathered information about the state of the corona and the magnetic fields in the photosphere--the lower layer of the sun's gaseous surface. Combining the SOHO data with the other observations will help piece together a better picture of the sun's magnetic structure as a whole.

It will be months before all the data is interpreted. But the researchers are already issuing a plethora of spectacular images that illuminate the sun's blaze in wavelengths from x-ray to the infrared. These new glimpses of old Sol instill the same awe that early humans must have felt when the corona suddenly burst into a dark sky as a ring of fire. And there won't be another in North American until August 2017.

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